@Override
public void visit(NodeTraversal t, Node n, Node parent) {
// Do the checks when 'n' is the block node and 'parent' is the function
// node, so that getControlFlowGraph will return the graph inside
// the function, rather than the graph of the enclosing scope.
if (hasReturnDeclaredNullable(n) && !canReturnNull(t.getControlFlowGraph())) {
String fnName = NodeUtil.getNearestFunctionName(parent);
if (fnName != null && !fnName.isEmpty()) {
compiler.report(t.makeError(parent, NULLABLE_RETURN_WITH_NAME, fnName));
} else {
compiler.report(t.makeError(parent, NULLABLE_RETURN));
}
}
}
/**
* @return True if n is a function node which is explicitly annotated as returning a nullable
* type, other than {?}.
*/
private static boolean isReturnTypeNullable(Node n) {
if (n == null || !n.isFunction()) {
return false;
}
FunctionType functionType = n.getJSType().toMaybeFunctionType();
if (functionType == null) {
// If the JSDoc declares a non-function type on a function node, we still shouldn't crash.
return false;
}
JSType returnType = functionType.getReturnType();
if (returnType == null || returnType.isUnknownType() || !returnType.isNullable()) {
return false;
}
JSDocInfo info = NodeUtil.getBestJSDocInfo(n);
return info != null && info.hasReturnType();
}